A hybrid vehicle is a vehicle that operates on multiple sources of energy. Of the various types of hybrid vehicles, fuel-electric hybrid vehicles are equipped with an engine that generates power through fuel combustion and a rechargeable energy storage system, e.g. a battery, that feeds power to a motor. Hybrid vehicles typically operate at reduced noise levels, have more efficient fuel consumption, and have lower emissions than conventional vehicles. Accordingly, increasing effort is being dedicated to the development of hybrid vehicles.
In conventional power transmissions for hybrid vehicles, an engine, a generator, and a first planetary gear set are connected to a first shaft and a motor, a second planetary gear set, and a differential unit are connected to a second shaft. The first planetary gear set and the second planetary gear set are connected via a power transmission unit having a plurality of gears. In this manner, power is routed from the engine through the first shaft to the first planetary gear set, then from the first planetary gear set to the gears of the power transmission unit and onto the second planetary gear set. From the second planetary gear set, power then flows through the second shaft to the differential unit, which in turn drives the wheels. The power transmission unit is therefore a necessary component in transferring power from the engine to the wheels in conventional power transmission systems.
Due to the complex gear engagement mechanisms, the conventional power transmission unit is heavy and bulky, thereby detracting from the fuel efficiency that a hybrid vehicle may achieve. In addition, installation and removal of the generator and motor are difficult because of the complex engagements of the plurality of gears.
The above information is provided only to enhance understanding of the background of the invention and not to be construed as a representation of prior art with respect to the present invention.